1. Field of the Invention
This invention relates to an external lead terminal adaptor for a semiconductor device, such as a power transistor module, and to a semiconductor device in which such an adaptor is used.
2. Description of the Related Art
In a power transistor module, such components as a transistor chip, external lead terminals connected to the transistor chip, and the like are incorporated in a sealed resin package in a manner so that the tips of the external lead terminals are presented on the upper face of a cover for the package. In order to obtain as much creepage insulation distance as possible between the terminals, generally, such a power transistor module is constructed so that the top of the package cover is stepped to provide vertically spaced upper and lower surface portions with the tips of external lead terminals arranged on both surface portions.
When a power transistor module of this type is used to provide an electronic device, such as an inverter, in order to reduce the size of the device, a printed circuit board, on which a snubber circuit and a driver, for example, are mounted, is commonly screwed directly to the upper face of the transistor module. The circuits on the printed circuit board are then electrically connected with the external lead terminals of the transistor module. However, because the external lead terminals of the power transistor module are not located in the same plane, but in planes at different levels, the external wiring between the printed circuit board and the transistor module require provision of wiring bars which are bent in accordance with the levels of the terminals, for example, thereby increasing manufacturing costs. This requirement may be avoided with an improved configuration wherein the cover for the transistor module package is made flat so that all external lead terminals are arranged in the same plane. However, this design gives rise to other problems such as redesign of the package and cover, the insulating characteristics thereof, requires additional costs, and hence is not advantageous.